Air bags have become common in modern automobiles. An air bag module including an inflatable cushion and an inflator is installed in the desired position within the vehicle. The cushion is stored in a folded position within the air bag module. In response to a threshold event or occurrence, a sensor provides a signal for activating the inflator. The inflator provides a supply of inflating gas to the cushion to inflate the cushion.
There are several types of inflators for air bag modules. One type is the pure gas inflator wherein a pressure vessel contains stored pressurized gas. The pressure vessel communicates with the cushion through various types of rupturable outlets or diaphragms. Another type is the gas generator wherein a propellant is ignited and the resultant gas flow through an outlet to the cushion. A third type is the hybrid or augmented type. This type includes a pressure vessel containing stored pressurized gas and a gas generator. When the generator is ignited, the resultant gas flows with the stored gas to the cushion through the pressure vessel outlet.
In some applications there are vents in the inflatable cushion that allow the inflation gas to escape the confinements of the bag. These vents allow for egress of the inflation gas as the pressure builds up inside the cushion. Typically, these vents are open at all times during a deployment or inflation of the air bag.